The mobile terminal usually includes a SIM card tray or socket for the installation of a SIM card. The SIM card may be inserted in the SIM card tray, or the SIM card tray may have a cover for fixing the SIM card. For example, a multi-function electronic device may include a card socket for SIM card, and thus the electronic device has to define an installation hole for the card socket, which may influence the structural integrity of the electronic device. A gap may exist at the position of the card socket, which may cause the problem of water leakage and poor structural strength. Furthermore, due to fabrication error during actual production, the card socket for SIM card may have several problems such as metal burr, installation defects and color aberration. The SIM card installed on the SIM card socket or card tray sometimes may not be identified if the clips in the SIM card socket or card tray is in poor contact with the SIM card.